A fuel cell is a cell which can obtain electricity in a process in which water is obtained by making hydrogen and oxygen react by utilizing a principle which is opposite of electrolysis of water. Generally, fuel gas is replaced with hydrogen, and air or an oxidizing agent gas is replaced with oxygen.
As such a fuel cell, for example; Japanese Patent Application Laid-Open (JP-A) No. 2000-123848 “Fuel Cell” is known. This fuel cell is shown by an exploded perspective view in FIG. 22.
As shown in FIG. 22, an anode side electrode 202 and a cathode side electrode 203 are disposed along an electrolytic film 201, and a unit fuel cell (cell module) 200 is structured by sandwiching these by a first separator 206 and a second separator 207 via gaskets 204, 205.
In detail, this is a structure in which a first flow path 208 which is a flow path for fuel gas is formed on a surface 206a of the first separator 206, and a second flow path 209 which is a flow path for an oxidizing agent gas is formed on a surface 207a of the second separator 207, and the fuel gas and the oxidizing agent gas respectively face the central electrolytic film 201.
Because the electric output which is obtained by one cell module shown in FIG. 22 is extremely small, by laminating a large number of such cell modules 200, the desired electric output is obtained. Accordingly, the first and second separators 206, 207 are called “separators” because the fuel gas and the oxidizing agent gas are separated so as not to leak to adjacent cells.
The first separator 206 has the flow path 208 for fuel gas on the surface 206a, and the second separator 207 has the flow path 209 for oxidizing agent gas on the surface 207a. However, it is necessary for gas to effectively contact the anode side electrode 202 and the cathode side electrode 203. Therefore, it is necessary for the flow paths 208, 209 to provide a large number of extremely shallow grooves.
Each of the first and second separators 206, 207, respectively, has a fuel gas supplying hole portion 210a and an oxidizing agent gas supplying hole portion 211a at one end portion thereof, and has a fuel gas discharging hole portion 210b and an oxidizing agent gas discharging hole portion 211b at the other end portion thereof. Further, each of the first and second separators 206, 207 has a cooling water supplying hole portion 212a for making cooling water pass through at one end portion thereof, and has a cooling water discharging hole portion 212b at the other end portion thereof.
The present inventor variously attempted to manufacture a cell module by sandwiching a membrane/electrode assembly formed from electrolytic films and electrodes by two separators, by coating on the separator a liquid sealant in place of the gaskets 204, 205 whose manufacturing requires much time and much cost. In this process, one problem arose. This problem will be described on the basis of FIGS. 23A and 23B which are schematic diagrams of the coating-start portion of the sealant.
As shown in FIG. 23A, when a sealant 222 starts to be coated on a separator 223 by moving a nozzle 221 in the direction of the outlined arrow while discharging the sealant 222 from the nozzle 221, because the adhesion between the separator 223 and a coating-start portion 224 of the sealant 222 is not sufficient, there are cases in which the distal end of the coating-start portion 224 turns up.
Further, as shown in FIG. 23B, because the nozzle moving velocity in the direction of the outlined arrow at the time of starting of coating of the sealant 222 is not appropriate, there are cases in which a missing portion 225 arises due to the coating-start portion 224 of the sealant 222 being cut off.
In this way, if the sealant coating quality of the coating-start portion 224 of the sealant 222 is reduced, the sealability deteriorates, and the sealant coating quality at the coated portion after the coating-start portion 224 of the sealant 222 is affected.
Yet another problem arose. This other problem will be described on the basis of FIGS. 24A through 24C in which the sealant is shown in cross-section.
As shown in (a) of FIG. 24A, the sealant 222 was coated on the separator 223. The sealant 222 has a height h1.
Next, as shown in (b) of FIG. 24A, an unillustrated membrane/electrode assembly and another separator 233 are laminated on the separator 223, and the sealant 222 is crushed until the height thereof becomes a height h2. The height h2 of the crushed sealant 222 is determined by the thickness of the electrolytic film and the electrode which are sandwiched between the separators 223, 223. In other words, because the electrolytic film and the electrode are between the separators 223, 223, the sealant 222 cannot be further crushed and extended. In the drawing, d1 shows the crushing margin of the sealant 222.
On the other hand, as shown in (a) of FIG. 24B, a sealant 235, whose height in cross-section is different from that of the sealant 222 in (a) of FIG. 24A, is coated on the separator 223. A height h3 of the sealant 235 is made greater than the height h1 of the sealant 222.
Next, as shown in (b) of FIG. 24B, the unillustrated membrane/electrode assembly and other separator 233 were laminated on the separator 223, and the sealant 235 was crushed until the height thereof became the same height as the height h2 of the sealant 222 in (b) of FIG. 24A. In this case, the crushing margin of the sealant 235 is d2.
In this way, given that the crushing margin of the sealant 235 is d2, the height h1 of the sealant 222 in (a) of FIG. 24A is smaller than the height h3 of the sealant 235 in (a) of FIG. 24B, and the crushing margin d1 is smaller than the crushing margin d2. As a result, at the sealant 222, the crushing pressure is insufficient, and it is difficult to obtain good sealability.
Here, in order to make the height of the sealant at the time of coating large, a sealant 237, as shown in (a) of FIG. 24C, in which the aspect ratio (the ratio between the height and the width) is made the same as the cross-section of the sealant 222 in (a) of FIG. 24A and the height is made the same as the height h3 of the sealant 235 in (a) of FIG. 24B, is used, and the sealant 237 is crushed as shown in (b) of FIG. 24C up to the height h2 which is the same as the height of the sealant 235 in (b) of FIG. 24B.
As can be understood from FIGS. 24B and 24C, the sealant 235 has a width w1, and the sealant 235 after being crushed has a width w2. On the other hand, a width w3 of the sealant 237 is greater than the width w1 of the sealant 235, and a width w4 of the sealant 237 after being crushed is greater than the width w2 of the sealant 235 after being crushed. If the width w4 of the sealant 237 after being crushed is too large in this way, there are cases in which the sealing quality is reduced due to the sealant 237 being forced out from a predetermined range between the separator 223 and the separator 233 which are laminated, or the output of the fuel cell is affected due to the sealant 237 adhering to the membrane/electrode assembly, and thereby deterioration of the quality of the fuel cell is brought about.